Thankfully there’s a ton of workarounds for that.

If there’s a tape deck, you can do headphone jack to cassette tape. If you don’t have a headphone jack on your phone you can get a little bluetooth reciever to headphone jack type thing.

There’s also the route of using a small device to broadcast your own little AM station (same deal, gets audio from jack or bluetooth), then tune into it with your existing head unit.

Best way is to just rig up your own aux in, but that requires some doing.